Dear doctor; I have been troubled by a small lump in my left armpit over the past two months. It is quite small but occasionally causes me some pain. Is it something serious or could it just be a broken sore? Mike Dear Mike, Your lump is most likely to be a small sebaceous cyst. These are usually situated just under the skin, and can easily become infected via a hair follicle. When infection occurs they tend to become tender. In most cases the infection will clear spontaneously, but sometimes antibiotics will be required, and occasionally the infected cyst will need to be drained surgically. Another possible cause of a lump in the armpit is an enlarged lymph gland. This might be due to a minor skin infection, perhaps picked up while shaving under the arms. Lymph glands are a normal part of the immune system’s defence against infection. When glands have become enlarged it usually takes several weeks for them to return to their usual imperceptible size. It is unlikely that the lump you have found has a more serious cause, but since it has been there for several months it would be wise to see your GP. He or she will be able to ask further questions and examine the lump. If it is thought to be a lymph gland your GP will also want to examine your breasts and possibly to organise a blood test.
